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Relation between Area of Opening and Range of Splash of Testing Fluid during Hydro Testing of Knife Gate Valve

International Journal of Trend in Scientific Research and Development (IJTSRD)
Volume 5 Issue 1, November-December
December 2020 Available Online: www.ijtsrd.com e-ISSN: 2456 – 6470
Relation between
etween Area of Opening and
nd Range of Splash of
Testing Fluid during
uring Hydro Testing off Knife Gate Valve
Gourav Vivek Kulkarni
Design and
nd Development Engineer, Expert Valve and
nd Equipment Private Limited, Belagavi, Karnataka, India
How to cite this paper:
paper Gourav Vivek
Kulkarni "Relation between Area of
Opening and Range of Splash of Testing
Fluid during Hydro Testing of Knife Gate
Valve" Published in
International
Journal of Trend in
Scientific Research
and Development
(ijtsrd), ISSN: 24562456
IJTSRD35781
6470, Volume-5
Volume
|
Issue-1,
1, December
2020,
pp.1
pp.1-4,
URL:
www.ijtsrd.com/papers/ijtsrd35781.pdf
ABSTRACT
Determination of relations between various variables is necessary while
designing any experiment. Various methods may be employed depending
on the availability of resources at the experimental setup. However, while
the experiment is being designed, it is equally important that the same is
backed by theoretical formulae. If not derived or proved already, new ones
can definitely be derived using first principles. In this study, a relation
between the area of opening and
nd range of splash shall be derived. The aim
of this relation shall be to get a basic comprehension of the variation in
parameters in relation to the range of splash of testing fluid. The concepts
of range of splash and area of opening shall be reported at the initial stage.
The area of opening shall then be determined using the method of
integration considering variables involved in the formulation. On obtaining
an expression, a relation between the area of opening and the range of
splash shall be derived. Towards the end a conclusion shall be drawn
reporting the proportional relations between the variables.
Copyright © 2020
20
by author(s) and
International Journal of Trend in
Scientific Research and Development
Journal. This is an Open Access article
distributed
under
the terms of the
Creative Commons
Attribution License (CC BY 4.0)
KEYWORDS: Range, area, splash, hydro, testing
(http://creativecommons.org/licenses/by/4.0)
A. Introduction to Knife Gate Valves
Knife gate valves belong to the family of block valves
which may also be known as on-off
off valves. These valves
are primarily used in demanding applications like
sludge, slurry, pulp, paper and so on where the working
fluids are relatively thicker and need to be cut through
with the aid of a knife gate. These valves are available in
metal seat and soft seat options according to the
requirement of the application. Various types of
actuations like manual, pneumatic, gear and motorized
electrical modes make these valves one of the most
versatile and sought after for the stated applications.
B. Range of splash of testing fluid
During hydro testing of Knife Gate Valves, after
completion of the Shell test and the Seat test, there is
another test that can be performed qualitatively to
confirm the performance parameters. This test
comprises of pressurizing the valve at the upstream and
opening the gate under this pressurized condition.
C. Area of opening creating a splash
Area of opening refers to the geometrical area opening
responsible for the flow. In case of Knife Gate Valves,
since the bore and gate have
ve circular edges, the area is
completely bounded by regular curves which are arcs.
This makes it easier to evaluate the area as the
equations of arcs are quite handy during the process of
finding the area.
Following figures indicate the generation of flow
flo areas
at different degree or percentage of opening of the gate.
The origin shall be considered as the reference and the
same shall be coinciding with the bore center of the
valve. Every figure comprises of a circle indicating the
valve bore and an arc indicating
dicating the gate edge. The
shaded area is the topic of interest in this interest.
The first consideration is as follows.
While doing so, at the
e instant when an opening is
created by virtue of motion of the gate, there is a splash
of testing fluid that can be observed to land at a certain
distance. The horizontal distance covered by the splash
is termed as the range of the splash. This paper shall
shal try
to establish a relation between the range of splash and
the area of opening.
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35781
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International Journal of Trend in Scientific Research and Development (IJTSRD) @ www.ijtsrd.com eISSN: 2456-6470
The figure depicts minimum percentage of opening and
the area of flow generated thereby. The points of
intersection of the two curves are distinct, do not lie on
any axes and their intercepts form the boundaries or
limits of integration while determining the flow area of
opening. The shaded area can be determined by finding
the difference between the area enclosed by the semi
circle and the curve with respect o the abscissa
between the limits. Since both the areas are on the
same side of the abscissa, modulus of the area may or
may not be considered while adding the same.
The second consideration is as follows
The figure depicts approximately a quarter of
movement of gate opening and the area of flow
generated thereby. The points of intersection of the two
curves are distinct, do not lie on any axes and their
intercepts form the boundaries or limits of integration
while determining the flow area of opening. The shaded
area can be determined by finding the difference
between the area enclosed by the semi circle and the
curve with respect o the abscissa between the limits.
Since both the areas are on the same side of the
abscissa, modulus of the area may or may not be
considered while adding the same.
The third consideration is as follows
The figure depicts a point in time where the edges of
the gate are collinear with the origin. The points of
intersection of the two curves coincide with the
abscissa thereby marking the boundaries or limits of
integration to be the points on the circumference of the
circle indicating the bore. The shaded area can be
determined by finding the difference between the area
enclosed by the semi circle and the curve with respect o
the abscissa between the limits. Since both the areas are
on the same side of the abscissa, modulus of the area
may or may not be considered while adding the same.
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The fourth consideration is as follows
The figure depicts a point in time when the edge of the
gate coincides with the origin. The points of
intersection of the curves are distinct but in this case,
the intercepts cannot be considered as the boundaries
or limits of integration as certain definite or
considerable area is lost while doing so. In this case and
for further opening, while calculating the area, two
different sets of integrals need to be considered based
on the location of the point. For the third and fourth
quadrants, the area is equal to half that of the bore. The
areas in the first and second quadrant are symmetrical
hence an arithmetic sum can be taken. A further
division into two sets of areas, one bounded from the
origin to the intercept corresponding to the point of
intersection and the other from the intercept
corresponding to the point of intersection to the radius
of the circle need to be considered and calculated
accordingly in order to obtain the total area.
Thus considering the scope of study, a little
consideration will show that only the first figure would
be applicable. Thus the remaining three figures shall be
out of purview of this paper.
D. Determination of area of opening
Consider the following figure.
Let the valve bore be indicated by a circle of radius ‘r’
with its centre at the origin. Equation of the circle is
given by.
+
=
…..(1)
This circle shall indicate the flow area. The lowermost
tip shall be the closing position and the uppermost tip
shall be the open position.
Consider an arc indicating the gate edge of radius ‘a’
with its centre located at an eccentricity ‘e’ from the
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International Journal of Trend in Scientific Research and Development (IJTSRD) @ www.ijtsrd.com eISSN: 2456-6470
origin at a given instant. Since the arc is a part of the
circle, the equation is given by.
+( − ) =
…..(2)
Area enclosed by the curve indicating the bore, abscissa
between the points of intersection is given by.
.
=
√ −
…..(5)
This equation can be written considering the circle to
be at a centre other than origin, (0,e) in this case with a
radius a units.
Area enclosed by the curve indicating the gate edge,
abscissa between the points of intersection is given by.
.
=
−
−
+
…..(6)
The area of opening can be determined by the method
of integration by considering the intersection of these
two curves.
Since two circles intersect at two points, symmetry can
aid the ease of calculations and formulations. The
points of intersection can be determined by solving the
two equations. However while doing so theoretically,
the arbitrary constants may not provide the
coordinates of points of intersection. But during actual
determination using the constants, the coordinates of
points of intersection can directly be obtained.
In order to proceed with the derivation for the
expression, the coordinates of points on intersection
can be determined logically. It is clear from the figure
that the point of intersection is at a polar radius of ‘r’
from the origin. This is applicable to any level of
opening at the two curves would always intersect on
the circumference of the circle indicating the bore.
Thus the coordinates of the point of intersection in
polar system can be written as (r,-θ) and (r,θ). Here, the
angle θ indicates the inclination of the radius with
respect to the origin. As per the general convention, the
angle considered in the clockwise sense shall be
negative and that in the anticlockwise sense shall be
positive. A little consideration will show that the angle
of inclination is proportional to the eccentricity. This
can aid in the numerical determination of the angle.
As an alternative, if Cartesian coordinates
considered, the same can be identified as
(r.cosθ,-r.sinθ) and (-r.cosθ,-r.sinθ)
are
These points shall be the limits of integration in the
expression.
Since the figure is symmetric about the ordinate, the
ordinate shall be considered for evaluation of the
integral and the abscissa shall be the reference axis.
From Equation (1),
+
=
=√ −
…..(3)
From Equation (2),
+( − ) =
+
+
−
=
=
−
−
+
|
Required area,
=
.
(
√ −
.
−
−
−
+
)…..(7)
Thus further solution of Equation (7) gives the area of
opening of the valve at the required instant. The radii
can are known and the eccentricity depends on the
degree of opening.
Relation between area of opening and range of splash
In this section, a relation shall be derived relating the
range of splash and the area of opening.
According to the Hydrostatic law, the Pressure ‘P’ can
be expressed in terms of an equivalent head ‘H’
P = ρ . g. H
…..(8)
Where ρ = Density of flow media
g = Acceleration due to gravity
H = Height of fluid column i.e. head
On further simplification,
H = P / (ρ . g) …..(9)
Thus the head corresponding to the line pressure can
be calculated.
For flow through orifices, corresponding to a head ‘H’,
the velocity of flow through the orifice can be given by
the following expression available in literature[1].
=
. . …..(10)
The discharge of fluid through the opening of area A as
calculated using Equation (7) and the flow velocity is
given by.
Q = AV …..(11)
The hydraulic power available at the upstream is a
product of the pressure and discharge.
Power, W = ρ . g . Q . H …..(12)
…..(4)
The required area of opening is the difference between
areas individually enclosed between the two curves
within the limits defined by the points of intersection of
the curves.
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The difference between these areas can provide the
expression for the area of opening which is more or less
always in a crescent shape.
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On rearranging the terms on both sides after
substitution,
=
…..(13)
. . .
Range of splash, [3]
= .
. …..(14)
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International Journal of Trend in Scientific Research and Development (IJTSRD) @ www.ijtsrd.com eISSN: 2456-6470
Substituting Equation (13) in Equation (14),
.
.
=
…..(15)
. . .
This is the required expression that gives the relation
between the area of opening and the range of splash.
As the hydraulic power increases, the range is said to
increase proportional to the amount of fluid being
discharged.
As the density of testing fluid increases, the range of
splash decreases due to the tendency of the fluid to
cover a shorter range on account of its inertia.
Range of splash and the area of flow are inversely
proportional. At the instant of opening, there is an
infinitesimal area of opening which can lead to the
maximum range of splash. As the percentage of opening
increases, the area also increases proportionately but
the pressure reduces, thereby leading to an increase in
the discharge. The properties of cohesiveness and fluid
viscosity tend the splash to be generated with a shorter
range.
Conclusion
Thus it can be concluded that considering the area of
opening, the range of splash of testing fluid is directly
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proportional to the hydraulic power and the time interval
while it is inversely proportional to the density of the fluid,
area of opening and the hydrostatic head. Thus a relation
has been established theoretically.
Acknowledgement
The author sincerely thanks Management and staff of
Expert Valve and Equipment Private Limited, Belagavi,
Karnataka for their continuous support.
References
[1] Dr. R. K. Bansal, "A Textbook of Fluid Mechanics and
Hydraulic Machines", Laxmi Publications (P) Ltd,
Ninth Edition, 2014, ISBN: 978-81-318-0815-3
[2]
Prof. V. Ranganayaki Rao, Prof. M. Y. Viswanatha
Sastry, Prof. M. Gururaja, "A Text Book of Physics",
Model Educational Series Publications, 2010 Edition
[3]
Gourav Vivek Kulkarni "Determination of Range of
Splash of Testing Fluid during Hydro Testing of
Knife Gate Valve" Published in International Journal
of Trend in Scientific Research and Development
(ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-6,
October
2020,
pp.1686-1688,
URL:
https://www.ijtsrd.com/papers/ijtsrd35747.pdf
Volume – 5 | Issue – 1
|
November-December 2020
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